Persistent global marine euxinia in the early Silurian.

ABSTRACT: The second pulse of the Late Ordovician mass extinction occurred around the Hirnantian-Rhuddanian boundary (~444?Ma) and has been correlated with expanded marine anoxia lasting into the earliest Silurian. Characterization of the Hirnantian ocean anoxic event has focused on the onset of anoxia, with global reconstructions based on carbonate ?238U modeling. However, there have been limited attempts to quantify uncertainty in metal isotope mass balance approaches. Here, we probabilistically evaluate coupled metal isotopes and sedimentary archives to increase constraint. We present iron speciation, metal concentration, ?98Mo and ?238U measurements of Rhuddanian black shales from the Murzuq Basin, Libya. We evaluate these data (and published carbonate ?238U data) with a coupled stochastic mass balance model. Combined statistical analysis of metal isotopes and sedimentary sinks provides uncertainty-bounded constraints on the intensity of Hirnantian-Rhuddanian euxinia. This work extends the duration of anoxia to >3 Myrs - notably longer than well-studied Mesozoic ocean anoxic events.

SUBMITTER: Stockey RG 

PROVIDER: S-EPMC7156380 | biostudies-literature | 2020 Apr

REPOSITORIES: biostudies-literature